Rock drill



L. A; B. HUTTON- 2,307,507

ROGK DRILL Filed July 1, 1942 A TT'OR/VEX katen dlaaaima v ROCK DRILL Lionel Alfred Bennett-Hutton, Ottawa, Ontario,

' Canada Application July 1, 1942, Serial No. 449,233 In Canada February 23. 1942 Claims. (01. 287-119) This invention relates to rock drills of the type comprising a shank and a detachable bit and more particularly to means for securing the bit to the shank.

The advantages of employing detachable bits on drill shanks have long been recognized and many types of detachable bits have been proposed.

These bits have, however, frequently been subject to disadvantageous features such as high cost of manufacture, complication of structure, and constructional weakness under the stresses to which they are subjected. These disadvantageous features are usualLv incident to the means provided for securing the bit to the shank. Moreover, as in all cases the shank must be machined to fit the bit closely, problems in machining present themselves whenthe design is of a complicated nature. In such instances, it is usually necessary to bring the shank to the surface of the mine for the machining operation.

It is the object of the present invention to provide a rock drill having a bit and an interengaging shank portion of relatively simple design and manufacture, the bit and shank having complementary surfaces adapted to provide a plurality of areas of frictional contact of the shank with the bit upon partial rotation withrespect The inner surface Figures 17 and 18 are sectional elevations illustrating additional features of the invention,

Figure 19 is a transverse section on line Iii-l9 of Figure 18, and

Figure 20 is a sectional elevation showing a further feature of the invention.

Referring to Figures 1 and 2, a cylindrical bit i havinga socket 2 to receive a shank 3 is shown. of the bit is provided with four arcuate portions 4, the geometrical centres of which are indicated at 5.

, from the longitudinal axis of the bit, the radii of to each other. To this end, the invention comprises broadly the provision of a rock drill mema her having a surface adapted to present a plurality of areas of frictional contact with the surface of a second member upon partial rota-- tion of one member'relatively tothe other, such first surface having a plurality of arcuate portions, the geometricalcentres of which are each located at difierent points. The-invention may also be said to reside in the provision of a substantially cylindrical rock drill member having a surface provided with a plurality of arcuate portions, the geometrical centres of which are each offset from the longitudinal axis of the member.

Other objects, advantages and structural details of the invention will become apparent from the following description with particular reference to the accompanying drawing, in which:

Figures 1 to 16, inclusive, are transverse sections of various forms of rock drills constructed in accordance with the invention, Figures 1, 3, 5,

7, 9, 11, 13 and 15 each showing two members of a drill in interfitting but non-frictional relation with each other, and Figures 2, 4, 6,8, 10, 12, 14 and 16 each showing the two members of the respective forms in locked frictional contact with each other,

the arcuate portions beingequal. the arcuate portions are joined by 6. The shank comprises a plural The ends of flat surfaces sided or octagonal steel rod having its corners turned off about the same radius as that of the arcuate portions, to provide bit contacting arcuate surfaces I. As illustrated in Figure 2, rotation of the shank will result in frictional contact of the shank with the bit at four spaced areas, a wedging action being set up due to the inclination of the arcuate portions with respect to the axis of the drill. I

In Figures 3 and 4, the cylindrical bit 8 has a socket 9 to receive the shank Ill. The inner surface of the bit is again provided with four arcuate portions ll, having their geometrical centres indicated at l2. In this instance also, the centres are each offset, and spaced equidistantly, from the longitudinal axis of the drill, the radii of the portions being equal. It will be observed, however, that these centres are located on diameters of the drill, the centre of each alternate arcuate portion being located on a diameter at right angles to that of the adjacent portion. The ends of the arcuate portions are joined by flat surfaces l3. The shank is provided with complementary arcuate surfaces H and flat surfaces 15. As clearly shown in Figure 4, rotation of the shank with respect to the bit results in wedging contact therebetween at four spaced areas.

Referring 'to Figures 5 and 6, the cylindrical bit 16 is provided with a socket H to receive the shank 18. The inner surface of the socket is here provided with three arcuate portions l9, their geometrical centres being indicated at 20. In this instance again, the centres of the arcuate portions are each offset, and spaced equidistantly, from the longitudinal axis of the drill, the radii of the portions being equal. It will be noted that the arcuate portions intersect each other. The shank has three complementary arcuate surfaces 2|. As shown in Figure 6, rotation of the shank As shown, these centres geometrical centres of equal, and the centres are surfaces 52. The

with respect to the bit in either direction results in wedging contact at three spaced areas.

Referring to Figures '7 and 8, the bit 22 has a socket 23 to receive a shank 24. The inner surface of the socket is provided with four intersecting arcuate portions 25, the geometrical centres of which are represented at 26. Here again, the centres are each offset, and spaced equidistantly, from the longitudinal axis of the drill, and the radii of ,the portions are equal. As 1 in the form shown either direction with respect to the bit results ina wedging contact at four spaced areas, as shown in Figure 8.

In Figures 9 and 10, a bit 28 has a socket 28 to receive a shank 30. The inner surface of the socket has two arcuate portions 3| and 32, the which are indicated at 33 In this form, the centres are each offset, and spaced equidistantly, from the longitudinal axis of the drill, but the radii of the portions differ. The centres are, however, located on the same diameter of .the drill. It will be observed that the portion 3| of smaller radius extends throughout a complete semicircle, while the other portion extends throughout an arc of somewhat less extent. At one side of the socket, the adjacent ends of the arcuate portions intersect on the diameter on which the centres are located, but at the other side, the adjacent and 34, respectively.

, ends of the arcuate portions are joined by a flat surface 35. The shank has complementary arcuate surfaces 36 and 31 and a fiat-surface 38. Rotation of the shank with respect to the bit results in a relatively broad wedging contact at two spaced areas.

Referring to Figures 1land'l2, the cylindrical bit 39 has a socket 4|! with a shank 4i .therein. The inner surface of the socket has two arcuate portions 42, the centres of which are indicated 5 at 43. In this form, thec'entres are each offset, and spaced equidistantly, from the longitudinal axis of the drill,

located onthe same diameter of the drill. The adjacent ends of the arcuate portions, at either side, arejoined by flat portions 44. The shank has complementary arcu-' ate surfaces and flat surfaces, Here again, as in the form shown in Figures 9 and 10, rotation of the a relatively broad areas.

Referring to Figures 13 and 14, a bit 41 has a socket 48 with a shank 48 therein. The inner surface of the socket has two arcuate portions 50 with geometrical centres 5i offset equidistantly from the longitudinal axis of the drill but lowedging contact at two spaced thatoftheadja-f 40 to provide a allow the latter .to be withdrawn without distortthe radii of the portions are 0 diameter.

versed,'in which case the arcuate portions winintersect to thereby eliminate the connectini surfaces 52.

In Figures 15 and a socket 515 with a shank 51 therein. The inner surface of .the socket has two arcuate portions I. and 59 with geometrical centres Gland Shrespectively, each oifset from the longitudinal axis of the drill on the same As in the and 10,

portion of larger ra'dius excircle while'thepther an arc of somewhat less extent. At one side of the socket the-adjacent ends of the arcuate por- "tions intersect on the diameter on which the centres are located, but at the other side, the

adjacent ends of the portions are joined by a third arcuate surface 62. The latter surface may, however, be flat, as in the form shown in Figure 9.

The shank has complementary arcuate surfaces 63, 64 and 65. Rotation of the shank with re- While in the forms shown in Figures 9 and bit in but one position, in the other forms it may be inserted in two, three or four rotative positions with respect to the bit.

Figure 1'7 illustrates the assembled bit shank in elevation.

shank, such taper corresponding tothe normal taper on .the wall of the bit socket. As is well known in the art of drop forging and specifically in the step of forging a socket in a bit or other member by means of a male die, it is necessary draft or taper on such male die to ing the socket, since the die tends to expand by reason of the heat imparted by the member being forged and the latter tends .to contract as cooling commences whereby seizing of the die by the member may occur. The usual draft or taper on such male dies is from 3% to 12%. Provision of a taper on the shank of the same degree as that normally present on the bit socket wall results in a more uniform pressure between the shank and bit and thus avoids injury to the bit by application of great pressure at localized shank with respect to the bit results in 5 cated on the same diameter. It will be observed complete semicircle, their adjacent ends at either side being joined by short fiat, or slightly curved,

shank has complementary arcuate surfaces 53 and fiat or curved surfaces 54. Rotation of the-shank in either direction results in relatively wide wedging contact with the bit at two spaced areas. It will be apparent that the geometrical centres of the arcuate portions 50 may be offset in opposite directions and still achieve the desired wedging effect.

words, the centres of each portion may be re- "ll points.

Since the lower part of the bit is strongest, it is proposed to provide greatest pressure between tlie shank and bit socket adjacent the bottom thereof as in the form shown in Figures 18 and 19. In this form, the upper portion of the socket wall is provided with a pressure relief cutout portion 61 having ribs 68 adapted to have bearing contact with the shank. This cut-out portion relieves pressure on the weaker upper=end -of the bit while the ribs insure suflicient contact toprevent rocking of the bit on the hank. Instead of the bit having a socket to receive the shank, this arrangement may be reversed, as shown in Figure 20, with a shank l8 havingfia socket III to receive the portion II of a bit 12. In this form, the end of the shank is preferably upset to enlarge it as indicated at II whereby greater strength is provided in the socket portion. Chipways 14 are necessarily provided in the upset portion of the, shank.

The usual waterway 15 is provided in all forms.

7 The invention thus provides a simple but disc- 16, the cylindrical bit it has,

but spaced equidistantly form shown in Figures 9 the radii of the portions differ. However,

' in this instance, the tends throughout a substantially complete semiportion extends throughout and. A further important feature of the invention consistsfin the provision of a 3, taper 66 on the socket engaging portion of the .f

tive means for ensuring locking contact between bit and shank. It will be observed that in all cases, peripheral bearing contact between socket and shank is at a plurality of spaced points, rather than continuous as in many types of drills previously proposed. Such discontinuous peripheral contact is sufiicient to provide the necessary frictional engagement between shank and bit. The wedging action resulting from the structures described ensures that no relative movement between shank and bit takes place after looking contact is established. Removal of the bit from the shank is readily accomplished by reverse rotation of the members relative to each other un til they are in non-locking position.

Since the arcuate portions provided on the drill members represent in all cases true arcs of circles, the machining of the shank to desired shape is quite simple and may be accomplished without removing the drill steel from the mine.

A number of modifications of the invention have been illustrated and described in order to indicate the broad essential feature of the invention, namely, the provision of a plurality of arcuate portions inclined with respect to the axis of the drill members whereby on partial rotation of one member relatively to the other, a wedging action is set up efiecting frictional locking contact .of one member with the other. It will be apparent that various changes may be made in the described forms and other modifications developed without departing from the spirit and scope of the invention as defined in the appended claims.

I claim:

1. In a rock drill, a member having a socket in one end, and a second member having a shank fitting into said socket, said shank and socket each having a surface adapted to present a plurality of areas of locking contact with the surface of the other member, said surface of at least one of the members having a plurality of portions in the form of arcs the geometrical centres of which are located at different points, and also having at least one substantially fiat portion joining adjacent ends of said arcuate portions, said flat portion being substantially tangent to one of the arcuate portions.

2. A rock drill as defined in claim 1 wherein the radii of said arcuate portions are unequal.

3. In a rock drill, a member having a socket in one end, and a second member having a shank fitting into said socket, said shank and socket eachhaving a surface adapted to present a plurality of areas of locking contact with the surface of the other member, said surface of at least one of the members having a plurality of portions in the form of arcs, the geometrical centres of which are located at diiferent points, and a fiat portion joining the adjacent ends of said arcuate portions at one side of the member, the adjacent ends of said arcuate portions intersecting at the other side of the member.

4. In a rock drill, a member having a socket in one end, and a second member having a shank fitting into said socket, said shank and socket each having a surface adapted to present a plurality of areas of locking contact with the surface of the other member, said surface of at least one of the members having a plurality of portions in ,the form of arcs the geometrical centres of which are located at different points,

and also having a plurality of substantially fiat surfaces, each said flat surface joining a pair of adjacent ends of said arcuate portions and being substantially tangent to one of the arcuate portions.

5. In a rock drill, a member having a socket in one end and a second member having a shank at one end adapted to fit into said socket, said socket and shank each having a surface adapted to present a plurality of areas of locking contact with the surface of the other member, each said surface having two portions in the form of ares the radii of which are unequal and the geometrical centres of which are located at different points, and also having a substantially flat surface joining one pair of adjacent ends of said arcuate portions, said fiat surface being substantially tangent to one of the arcuate portions, the other pair of adjacent ends of said arcuate portions intersecting. I 6. A rock drill as defined in claim 5' wherein the smaller of said arcs extends throughout a substantially complete semicircle.

7. A rock drill as defined in claim 5 wherein the larger of said arcs extends throughout a substantially complete semicircle.

8. A rock drill bit having a socket in one end, said socket having a side wall surface comprising a plurality of portions in .the form of arcs, the geometrical centres of which are located at difierent points, and at least one substantially flat portion joining adjacent ends of said arcuate portions, said fiat portion being substantially tangent to one of the arcuate portions.

9. A rock drill bit of substantially cylindrical shape and having a socket in one end, said socket having a side wall surface comprising two portions in the form of arcs, the geometrical centres of which are located at different points but on the same diameter of said bit, and a substantially flat portion joining the adjacent ends of said arcuate portions at one side of the bit, the adjacent ends of said arcuate portions intersecting on said diameter at the other side of the bit.

10. In a rock drill, abit having a substantially cylindrical socket forged therein, the inner surface of the side wall of said socket having a taper extending outwardly from bottom to top thereof, said taper being of normal and of only sufiicient degree to permit the forging of the socket, a shank adapted to fit into the socket and having its outer side wall surface complementarily tapered whereby said latter surface may have continuous longitudinal engagement with the socket inner surface, the top portion of said socket inner surface having a cut-away portion to relieve contact pressure between said shank and socket at said top portion, said cutaway portion having a plurality of ribs extending throughout the same and longitudinally of the bit, the apexes of the ribs being flush with the bottom portion of said socket inner surface, each of said side wall surfaces having portions adapted to be placed in wedgingengagement with each 

